Earthquake Forecasting in recent large events in New Zealand

Matt Gerstenberger

GNS Science

Date & Time
Building 3, Rambo Auditorium
Sara McBride

The November 14th, 2016, Mw 7.8 Kaikoura earthquake generated significant shaking and damage throughout a large part of central New Zealand. The recovery effort has been distributed over a very large area and the dissemination of information about the potential for future shaking has been an integral part of the GNS Science response. Through the nature of the event and the varied recovery efforts we have been required to provide model results that spanned from aftershock probability tables through to detailed and specific engineering information. Additionally, the main shock triggered three slow slip events (SSE) on the Hikurangi subduction zone that were unique in character in our approximately 20 years of observations. These SSE have provided a difficult and interesting challenge to the ongoing forecasting efforts.

Our overriding philosophy remains that no single model sufficiently captures our current understanding of earthquake occurrence and that by using a hybrid of multiple models, we best capture the uncertainty in our knowledge of future quakes. To this point, and similar to past New Zealand earthquakes, we have used a hybrid forecast model based on the the STEP, ETAS, and EEPAS models, which we have combined with a range of long-term models, including a new strain-rate based model. We have used this hybrid model to produce forecasts from 1-day to 100-years. New Zealand end-users have become increasingly sophisticated in their uptake of forecasting information with increasing requests and needs from across sectors. A noticeable change in the Kaikoura response was the desire for forecast information not only to provided in seismic hazard terms, but in very specific risk terms for government and industry decision making.

In the past seven years, New Zealand has experienced around 15 large earthquakes which have required a forecasting response. In this presentation, I will discuss our forecast models, the engineering outputs developed, our efforts to estimate the impact of the SSE on the potential for triggered earthquakes.

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